T-tests
ST551 Lecture 10

Warm up: from last times slides:

A random sample of \(n = 25\) Corvallis residents had an average IQ score of 104. Assume a population variance of \(\sigma^2 = 225\). What’s the mean IQ for Corvallis residents? Is it plausible the mean for Corvallis residents is greater than 100?

Find point estimate, Z-stat and p-value, and 95% confidence interval

qnorm(0.975) = 1.96pnorm(1.33) = 0.9082409

Finish last time’s slides

t-tests

Inference for a population mean

What do we do if we don’t know \(\sigma^2\)? Realistically this is always the case